Chronic hyperglycemia causes ongoing oxidative stress and inflammation. When HbA1c exceeds 9.4%, these processes might plateau; thus, further increases in HbA1c won’t worsen them as much. This graph from the study shows the association between HbA1c and DR (red line). Blue bands represent the 95% confidence interval.

HbA1c level is known to be indicative as a critical biomarker for long-term glycemic control and is linked to risk of diabetic retinopathy development.

Researchers recently published a paper in BMC Ophthalmology in which HbA1c levels were measured and the association between this and DR was analyzed.

HbA1c positively correlated with DR; however, this was demonstrated by an inverted, U-shaped association, in which DR risk reached a peak of 9.4% with HbA1c level, then started to decline.

The authors explain that they found every 1% increase in HbA1c to be associated with a 7% increase in the odds of developing DR;

The investigators say, “Patients near the 9.4% HbA1c threshold need closer monitoring and timely intervention. For patients above 9.4%, consider aggressive glycemic control with complication monitoring.”


Ling J, Xie ZL, Chen XJ, et al. Inverted U-shaped relationship between HbA1c and diabetic retinopathy in diabetic patients: a cross-sectional study. BMC Ophthalmol. 2025;25:289.